1. Field of the Invention
The present invention relates to a tunable antenna and radio-frequency device, and more particularly, to a tunable antenna and radio-frequency device capable of changing radiation frequencies via connecting or disconnecting a coupling unit with a ground unit of the tunable antenna.
2. Description of the Prior Art
People traveling brings a demand of cross-area wireless service. In general, different telecommunication operators may utilize different wireless communication techniques, even though the wireless communication techniques are the same, operating frequencies may be different indifferent areas. Thus, a demand for a mobile device capable of supporting multiple wireless communication techniques and operating frequencies appears. Taking the Global System for Mobile Communications (GSM) for example, the following Table includes operating frequency ranges of GSM corresponding to different areas:
Global System for MobileFrequencyCommunications (GSM)Range (MHz)Area/Country800824-894USA19001850-1990900880-960Europe18001710-1880
Wireless communication devices are trending toward light weight and low profile, it is hence insufficient in antenna bandwidth. However, the lower frequency operation, the larger the antenna size is required for effective radiation.
Therefore, how to achieve multiple operating frequencies within a limited antenna dimension has become a goal in the wireless communication industry.